Installation for selectively dispatching articles



1964 A. EDELMAN 3,144,926

INSTALLATION FOR SELECTIVELY DISPATCHING ARTICLES Filed May 17, 1961 2Sheets-Sheet 1 BRANCH CoNvEY R N2 3 D|vERToR-\ 3 READING STA. N 3 6 BGIS 2 5 BRANCH CONVEYOR N 2 fi I thaw!- DIVERTOR 4 a] READING STA. N 2 0BRANCH CONVEYOR N l FIG. I FIG. 3 MAIN/ CONVEYOR 8f O O O O O C7/CD O O(T 0 o a u u u a u u is 7 FIG. 4

8b\ I 1 H 8b FIG. 6

8C INVENTOR.

FIG. 5 ABRAHAM EDELMAN 8b BY M A T TORNE Ys Aug. 18, 1964 A. EDELMAN3,144,926

INSTALLATION FOR SELECTIVELY DISPATCHING ARTICLES Filed May 17, 1961 2Sheets-Sheet 2 FIG. I2

INVENTOR.

ABRAHAM EDELMAN BY M ATTORNEYS United States Patent 3,144,926INSTALLATION FOR SELECTTVELY DISPATCHING ARTICLES Abraham Edelman, 12 E.22nd St, New York, N31. Filed May 17, 1961, Ser. No. 110,786 9 Claims.(Cl. 198-43) The present invention relates to an installation forselectively dispatching articles traveling on a conveyor to selectedreceiving conveyors, and more particularly, to a control system forautomatically diverting articles from a main conveyor to receivingstations selected by a dispatcher.

It is a broad object of the present invention to provide a novel andimproved control system of the general kind above referred to by meansof which the desired destination of the article can be convenientlyselected.

A more specific object of the invention is to provide a novel andimproved control system which permits a rapid and simple marking of thearticle for a selected destination and an equally rapid and simplechanging of the marking if it is desired to direct the article toanother destination.

Another more specific object of the invention is to provide a novel andimproved control system, the marking means of which allows a practicallyinfinite number of convenient and distinctive markings of the articlesto be dispatched to selected destinations.

Still another more specific object of the invention is to provide anovel and improved control system including sensing means which arehighly discriminatory in their response to marking patterns on articles,thus assuring that the marked articles are correctly directed toward theselected destinations.

The aforementioned objects, features and advantages of the invention andother objects, features and advantages which will be pointed outhereinafter are attained by providing on each article to be diverted toa selected destination an array of retrodirective reflectors, and one orseveral Reading Stations including one or several Sensors arrayed in apattern, each Sensor responsive to the reflectors of the pattern. Whenthe entire pattern of Sensors in a Reading Station is simultaneouslyactivated by a corresponding pattern of reflectors on a passing article,then the Reading Station controls a diverter and causes it to directsuch article toward a predetermined destination, but to fail to director divert the article when the pattern thereon is such that it fails toactivate all the Sensors of the Reading Station.

The term article as herein sometimes used, is intended to refer to thearticle itself, the packaging of the article, and containers or trays,etc. in which the articles may be placed while traveling on the conveyortoward a selected receiving station.

In the accompanying drawing, several preferred embodiments of theinvention are shown by way of illustration and not by way of limitation.

In the drawing:

FIG. 1 is a diagram of a dispatching installation according to theinvention;

FIG. 2 shows an article labeled with marking means according to theinvention;

FIG. 3 shows :an article labeled with a modified arrangement of themarking means;

FIG. 4 is a perspective view of a marking means in which the position ofthe reflectors is variable to form a selected reflector pattern;

FIG. 5 is a detail view of the marking means of FIG. 4;

FIG. 6 is a front view of FIG. 5;

FIG. 7 is a side view of a further modification of a marking meansincluding movably disposed reflectors;

FIG. 8 is a detail view of FIG. 7 on an enlarged scale;

3,144,926 Patented Aug. 18, 1964 FIG. 9 is a further modification of themarking means in which selected patterns may be formed by varying thereflection characteristics of selected ones of an array of reflectors;

FIG. 10 is a diagrammatic view of one of the sensing units of theinstallation;

FIG. 11 is a perspective diagrammatic view of a reading station and ofan article just reaching the reading station; an

FIG. 12 is a circuit diagram of a reading station forming part of thedispatching installation.

Referring first to FIG. 1 in detail, this figure shows a conventionaldispatching installation in conjunction with which the control systemaccording to the invention can be advantageously used.

The showing of the installation is generally self-explanatory. Thearticles to be directed to selected receiving stations are upon a mainconveyor 1 after having been appropriately marked by a dispatcher in adispatching station. The dispatching station is equipped to mark adesired pattern and to eliminate prior patterns. Three branch conveyorsare shown to lead off the main conveyor and, depending upon the positionof the Diverter associated with each branch conveyor, an article eithercontinues to travel on the main conveyor or is diverted to the selectedbranch conveyor on which it travels to a receiving station. DivertersNos. 1 and 3 are positioned to direct articles to the respective branchconveyor while Diverter No. 2 permits continued travel of articles onthe main conveyor. If desired, all the Diverters may, of course, be soset that all the articles will remain on the main conveyor which shouldbe visualized as also leading to a receiving station.

Some of the articles to be dispatched are indicated by blocks 2. Aspointed out before the term article as herein used is intended toencompass the articles themselves and also containers, trays, or skidsin which the articles proper may be placed. In other words, the termarticle designates the body or structure to which the patterndetermining the path of travel of the article is applied.

The position of each Diverter is controlled by the reading of thepattern on an article by the respective Reading Station. Three suchReading Stations are shown by way of example, one for each branchconveyor. Each Reading Station incorporates a predetermined pattern andwhen a passing article bears a corresponding pattern, the ReadingStation will cause movement of the Diverter from one position to theother, say from the position shown for the Diverter No. 2 into theposition shown for the Diverters 1 and 3. After passage of the article,the Reading Station will permit the return of the respective Diverter toits initial position. It is, of course, also possible and within thescope of the invention to utilize the reading of a pattern by a ReadingStation for performing upon an article the pattern of which hascorrespondence with the pattern of the Reading Station, an operationother than diverting the article. For instance, certain stamping,closing, rotating, displacing or addressing may be applied to thearticle.

The installation as hereinbefore described and the function thereof aregenerally conventional. The present invention is concerned with themeans by which reading of a pattern applied to an article is effected byand in a Reading Station.

Broadly speaking, the invention resides in providing on the article apattern of reflectors which return the light incident thereupon and assensing means in the Reading Station a combination of Sensors includingphotocells, each responsive to the light reflected by the reflectors inthe pattern and which when all simultaneously energized initiate theactuation of the respective Diverter.

More specifically, the invention uses as reflectors socalledretrodirective reflectors. Such reflectors return light incident upontheir reflecting surfaces in a direction which is substantiallyidentical with the direction of the incident light. Various types ofretrodirective reflectors are well known in the art and available in themarket. One kind of retrodirective reflector known by the trade nameStimsonite" uses three reflecting surfaces, mutually at right angles.The incident light is always reflected by such combination of surfacesso that it returns parallel to its incident direction. Another kind ofretrodirective reflector known by the trade name Scotchlite uses glassballs as lenses to concentrate the incident light to a focal area whichis highly reflective. The light is then reflected back on itself. Glassballs used for the purpose have, for example, a diameter of about 0.005and are adhered to the surface of a sheet of reflective material. Anyretrodirective reflector of the kind above referred to and other kindsknown and available in the market are suitable for the purpose of theinvention. The reflectors themselves do not constitute part of theinvention and are hence not described in detail.

Pattern Marking Means FIG. 2 shows an article 3 to which is adhered alabel 4. The label has attached thereto by silk-screening, painting,printing, etc., four retrodirective reflectors which constitute apattern capable of activating, for instance, Reading Station No. 1.Label 4 may, of course, be printed with appropriate information such asshipping instructions.

The dispatcher before placing the article on the main conveyor simplyselects a label bearing the appropriate pattern and adheres such labelto the article.

FIG. 3 shows an article 3 to which is applied a pattern formed by fouradhering reflectors 6. The reflectors may be attached to independentgummed labels Which can be applied by a group of conventional labelapplying machines each capable of attaching on selected or a pluralityof labels. Such a machine group can be controlled by a keyboard controlto form a selected pattern of reflectors. Machines suitable for thepurpose are well known in the art and the specific arrangement of suchmachine does not constitute part of the invention.

As is evident, the patterns as shown in FIGS. 2 and 3 are fixed once thereflectors have been applied to the article.

FIGS. 4, 5 and 6 show an arrangement which permits a convenient changingof the pattern. According to the arrangement of FIGS. 4 through 6 a tray7 has mounted on its side which will face the Reading Stations when thetray is placed upon the conveyor a pattern carrier 8. Branch 8a of thecarrier is secured at 8b to the side wall of tray 7 and bent off in itsmiddle portion to form a clearance 8c. The bight 8d includes a row ofapertures See, the purpose of which will be explained hereinafter andthe other branch 8 of the carrier constitutes an apron partly coveringbranch 8a.

The middle portion of branch 8a includes a plurality of slots 8g widenedat both ends to form detention openmg 811. The number of slots 8g isselected in accordance with the number of reflectors which it is desiredto have available for the selection of patterns. Eleven slots are shownby way of example. Accordingly, eleven openings 8e are also provided.Each of the slots accommodates a retrodirective reflector 9 of the kindpreviously described. Each reflector is held in a mount 10 which has achanneled cross section and is secured to a pin 11 terminating in aflange 11a. The end of pin 11 is enlarged at 11b, somewhat in the mannerof a screw head. A loaded coil spring 12 abutting against flange 11a andthe respective wall of branch 8a of the carrier urges the reflectorassembly 9, 10 toward branch 8a. Accordingly, the reflector assemblywill occupy the position shown in FIG. 5 when the reflector is in itsuppermost position and 4 will occupy a similar position when it is inits lowermost position. As is evident, the provision of enlargements 811in conjunction with pinhead 11b and spring 12 constitue a releasabledetention for the reflector assembly in either limit position thereof.

A reflector in its lowermost position is exposed to light incident uponthe pattern carrier, whereas the reflector in the uppermost position isshielded against such light.

In FIG. 4 three reflectors are shown in the exposed position and thesereflectors constitute the selected pattern. As is evident, a greatvariety of patterns can be selected by simply moving reflectors up ordown.

Setting of the reflectors in the upper or the lower position can beeffected by any suitable means, manually operated or by remote control.Such means may comprise an upper air nozzle 13 and a lower air nozzle 14for each reflector. Each upper air nozzle is disposed in alignment witha respective hole 86. As is evident, a flow of air under pressuredirected by nozzle 13 upon a reflector in the upper position will movesuch reflector into the lower position, and similarly an air blast bythe lower nozzle will lift a reflector. The control of the air flow tothe selected nozzle may be effected by a suitable pipe and valvearrangement in the dispatching station. Suitable controls installationsfor directing the flow of pressure air to selected nozzles are wellknown in the art and do not constitute part of the invention.

FIGS. 7 and 8 show another modification of an arrangement for selectinga pattern from an array of retrodirective selectors.

According to FIGS. 7 and 8, a tray 3a is placed upon main conveyor 1.The side wall of the tray facing the Reading Stations as the traytravels on the conveyor mounts a plurality of carriers, each supportingone retroactive reflector 15 of the kind previously described. Eachreflector is supported on one arm 16a of an angle bracket 16. Thebracket is secured to the tray pivotal about a pivot 17 so that thereflector carrier may occupy either the position of FIG. 7 or theposition of FIG. 8. The position of FIG. 7 is the active position of thereflector, that is, the reflector is positioned to reflect lightincident upon it from a sensing unit of a Reading Station as will bemore fully described hereinafter. In FIG. 8 the reflector is in itsinactive position, that is, the reflector is incapable of eflicientretrodirective reflection of light emanating from the sensing unit. Thereflector carrier is frictionally retained in either position by meansof springly detents 18 and 19 engageable with arms 16a and 16b,respectively, of bracket 16.

The bracket can be moved into one or the other position by means of anair stream directed by nozzles 20 and 20a upon one arm or the other ofthe bracket. As is apparent a blast of air directed by nozzle 20 uponarm 16a will pivot the reflector from the inactive position of FIG. 8into the active position of FIG. 7 and vice versa.

The flow of pressure air through nozzles 20 and 20:: should bevisualized as being controlled by the dispatcher by means of suitablecontrol valves and pipe connections as is well known.

By moving selected reflectors of the array on the tray into the activeposition and others into the inactive position a great variety ofreflector patterns may be formed on the tray.

In FIGS. 4 through 8 arrangements are shown in which a desired reflectorpattern is produced by varying the posi tion of selected reflectors inan array of reflectors. According to FIG. 9 the same result is attainedby rendering the surface of selected reflectors reflecting ornon-reflecting by coating or non-coating the surfaces of the reflectorswith a coating which will completely, or at least substantially, preventreflection of incident light. Such coating may be effected by directinga short burst of a spray of a suitable material such as a paraflinhaving a low melting point upon the reflector surface. A spray of liquidparaflin can be made to freeze into tiny droplets upon contact with thereflector surface. The coating may be removed in a similar manner byspraying a solvent upon the surface of the reflector which will dissolvethe paraffin or other coating, thereby restoring the reflectingproperties of the reflector. As is shown in FIG. 9, a plurality ofretrodirective reflectors 25 are fixedly secured to the wall of a tray3b, two reflectors of the array being visible.

The reflectors in the array may be arranged in two parallel rows, inwhich case two spray devices are sufficient to effect coating ofselected reflectors in each row, or removing the coating from selectedreflectors. The spraying arrangement is shown as comprising two spraynozzles 26 and 27, one for each row. Each nozzle is connected by a pipe28 and 29, respectively, to a supply container 30 which may contain asupply of paraflin 31 heated by a heating element 32. The flow ofparaflin through pipes 28 and 29 is controlled by solenoid valves 33 and34, respectively. The valves are normally closed and are opened when andwhile normally closed push button switches 35 and 36, respectively, areclosed. It is, of course, also possible to provide a remote control ofthe valves by remote control circuits well known for such and similarpurposes.

Removal of the coating from a coated reflector may be effected in thesame manner by using a suitable solvent instead of paraflin or othercoating material 31.

A desired pattern is produced by moving in the dispatcher stationreflectors to be coated into alignment with the spray nozzles and thenactivating the nozzles until a coating of the desired density is formed.Similarly, coatings are removed from the reflectors which are notselected to constitute part of the pattern.

In this connection it should be pointed out that in addition to thearrangements here shown, various other arrangements are feasible andwithin the scope of the invention to render active or inactive selectedreflectors constituting part of an array of reflectors.

Reading Stations Each Reading Station comprises a plurality of sensingunits. The number of the sensing units and the location thereof inreference to each other are so selected that the assembly of sensingunits in each Reading Station can respond to a definite series ofpatterns of reflectors only. It is, of course, possible to rearrange thesensing units so that the Reading Station can read a different pattern,but in any event, the arrangement of the sensing units must be such thatonly one series of patterns can be read at one time.

The sensing unit 40 of FIG. comprises a housing 41 supporting a sourceof light shown as a lamp 42 having an incandescent filament. The usefulpart of the light emanating from that lamp passes through a lightdeviating means 43 and strikes a retrodirective reflector 44 whichconstitutes part of a pattern to be read by the Reading Station, ofwhich the sensing unit 40 constitutes a part. The light deviating meansare shown as a beam splitter. Such beam splitter is, for example, amirror which is thinly silvered on the side facing reflector 44 and as aresult, the beam splitter passes part of the light of lamp 42 tothereflector and also deflects part of the light reflected upon it byreflector 44. The light deflected by the beam splitter is directed ontoa photocell 45 which is energized by the incident light.

As has been previously explained, it is characteristic for aretrodirective reflector that such reflector reflects the light in thesame direction as the light incident upon it. Accordingly, lightemanating from lamp 42 can reach photocell 45 only if such lightoriginates at lamp 42 and is reflected by the reflector 44 as only suchlight can reenter housing 41 in which beam splitter 43 and photocell 45are mounted. All stray light and all light reflected by reflectors otherthan reflector 44 will remain ineffective.

To confine the outgoing light into a narrow beam and to increase thelight available for the energization of photocell 45, condenser lenses46 or 47, or both, are preferably provided. Lens 47 concentrates thelight of lamp 42 and lens 46 focuses both the outgoing and the reflectedlight, causing the reflected light to focus upon the aperture 45a of thephotocell which is located at the image-point of the filament of lamp42.

The sensing units 40 of each Readingv Station are arranged andelectrically connected in accordance with the pattern of reflectors orgroup of such patterns, to be responded to by the Reading Station.

FIG. 11 shows a Reading Station which includes three sensing units 40.Two of these units are at the same level and the third one is somewhatlower, and all connected in series. Accordingly, the Reading Station isthereby arranged to respond to a pattern of three reflectors, two in onerow and a third one somewhat lower, and to larger patterns of which thepattern is a part. The article 2 traveling on the main conveyor carriessuch pattern. Accordingly, all three sensing units 40 will eachsimultaneously receive into their photocells 45 a large amount ofreflected light, as the article passes the Reading Station. As a resultof such simultaneous energization of all the sensing units, theactuating equipment 50 for actuating the Diverter associated with theReading Station will be operated, thereby moving the Diverter into theposition for diverting the article to the respective branch conveyor.After the article has passed the sensing units the photocells thereofbecome again de-energized, thereby permitting return of the Diverterinto its initial position, shown in FIG. 1 for Diverter No. 2.

The circuit diagram of the actuating equipment of the Reading Station isshown in FIG. 12. According to FIG. 12, the circuit system comprises apower supply 51. The lamps 42 of the three sensing units are connectedin parallel on a low-voltage secondary of a transformer 52. Thephotocells of the sensing units are connected in series to a DC. voltagesupplied by the transformer through a rectifier 53. The seriesconnection also includes the coil of a relay 54, the armature 55 ofwhich when attracted closes the circuit of solenoid coil 56. Thesolenoid is linked to a Diverter to pivot the same from the restposition shown in full lines into the diverting position shown in dottedlines. In actual practice, the solenoid may control an air valvecontrolling an air cylinder which in turn controls the flow of pressureair to control the position of the Diverter. Various other types ofconventional devices for controlling the position of the Diverter may,of course, also be used.

Each of the photocells of the system is the equivalent of a high megohmresistance when it is dark and the equivalent of a low resistance whenit is illuminated by light returned from a reflector. Consequently, ifany one of the three photocells in series is dark, the resistance thenincluded in the circuit of relay 54 is sufiicient to preventenergization of the relay. However, if all three photocells areilluminated simultaneously, the total resistance in series with relay 54is small enough to permit a current flow through the relay coilsufficient to energize the relay. As is evident from the previousdescription, all three photocells can be illuminated simultaneously onlywhen at least a portion of the reflective pattern on an article passinga Reading Station coincides with the arrangement of the sensing units insuch Reading Station, or in other words, if the article is one that wasintended to be diverted by that Reading Station.

It should be noted that the circuit of FIG. 12 is a simplified circuitto show the principle of the invention. In actual practice it may, andgenerally will, include amplifying circuits. It may also include delaycircuits to maintain the Diverter pivoted for a period of timesufficient to assure diversion of the article to a branch conveyor.Furthermore, the photocells may be connected in parallel, or series andparallel connections of the photocells may be combined.

While the invention has been described in detail with respect to certainnow preferred examples and embodiments of the invention it will beunderstood by those skilled in the art after understanding theinvention, that various changes and modifications may be made withoutdeparting from the spirit and scope of the invention, and it isintended, therefore, to cover all such changes and modifications in theappended claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. In an article-dispatching installation including a control system forcontrolling the diversion of articles travelling on a plane conveyor toselected receivers by actuating article diverters wherein said controlsystem comprises a selected pattern of several light reflectorsattachable to each article to be controlled and a reading means for eachof the diverters, each of said reading means comprising a physicalpattern formed by several sensing units for simultaneously sensing saidseveral reflectors of the pattern, each sensing unit including a sourceof light for directing a concentrated beam of light to a predeterminedone of the reflectors on the articles and a photocell electricallyresponsive to light and positioned to receive light reflected by therespective predetermined reflector only, said beams being parallel toeach other and to the plane of the conveyor, each reading means furtherincluding circuit means connecting the photocells of all the sensingunits forming the pattern of the respective reading means in anenergizing circuit and an electrically operated actuating means for eachof the diverters of the installation, said actuating means beingconnected to said energizing circuit and operated to actuate therespective diverter when all the photocells connected in the energizingcircuit become simultaneously electrically responsive by simultaneouslyreceiving light reflected from the respective reflectors of the patternof the reflectors, the light reflecting surface of each of saidreflectors being a retrodirective surface reflecting from each areaportion of the surface light impinging thereupon at any angle ofincidence parallel to such angle.

2. An installation according to claim 1, wherein each of said sensingunits comprises a light deviating means, the source of light of eachunit directing light upon the respective retrodirective reflectorthrough said light deviating means, and said light deviating meansdeflecting part of the light retodirectively reflected by said reflectorupon the respective photocell only to energize the same, and a lensmeans concentrating light emanating from the respective source of lightin a beam of light incident upon said light deviating means.

3. An installation according to claim 1, wherein each of said sensingunits comprises a light deviating means, the source of light of eachunit directing the light upon the respective retrodirective reflectorthrough said light deviating means, said light deviating meansdeflecting part,

of the light retrodirectively reflected by said reflector upon therespective photocell only to render the same electrically responsive.

, 4. An installation according to claim 3, wherein each of said lightdeviating means comprises a beam splitter.

5. An installation according to claim 1 wherein each of saidretrodirective reflecting surfaces is selectively changeable from areflective state to a non-reflective state and vice versa to form aselected pattern of surfaces in said retrodirectively reflective state.

6. A control system according to claim 5, and comprising mounting meanssupporting said reflectors in a fixed array, said mounting means beingattachable to an article to be controlled, means for applying toselected ones of said reflectors a reflection inhibiting coating, andmeans for removing such coating from a coated reflector to form aselected pattern of reflecting reflectors.

7. A control system according to claim 5, and comprising mounting meanssupporting said reflectors movable between a light reflecting positionand a nonreflecting position, said mounting means being attachable to anarticle to be controlled, and actuating means coacting with saidreflectors for moving selected ones from one position into the other toform a pattern of reflecting reflectors.

8. A control system according to claim 7, wherein said mounting meanscomprise a guide track each slidably guiding one of said reflectors,said reflectors being reflecting in one position on the respective guidetrack and n0nreflecting in another position on the guide track, andwherein said actuating means comprise nozzle means for directing a flowof pressure fluid upon a selected one of said reflectors to move thesame from one position into the other.

9. A control system according to claim 8, wherein said guide tracks arein the form of slots in a wall portion of said mounting means, andwherein retaining means are provided for each slot for releasablyretaining the respective reflector in either one of said positions.

References Cited in the file of this patent UNITED STATES PATENTS1,992,687 Anderson Feb. 26, 1935 2,000,403 Maul May 7, 1935 2,043,293Jennings June 9, 1936 2,294,930 Palrnquist Sept. 8, 1942 2,502,503Berkley Apr. 4, 1950 2,824,235 Hahn et a1 Feb. 18, 1958 2,922,893 EttJan. 26, 1960 2,998,117 Newburn Aug. 29, 1961 3,086,121 Cockrell Apr.16, 1963

1. IN AN ARTICLE-DISPATCHING INSTALLATION INCLUDING A CONTROL SYSTEM FORCONTROLLING THE DIVERSION OF ARTICLES TRAVELLING ON A PLANE CONVEYOR TOSELECTED RECEIVERS BY ACTUATING ARTICLE DIVERTERS WHEREIN SAID CONTROLSYSTEM COMPRISES A SELECTED PATTERN OF SEVERAL LIGHT REFLECTORSATTACHABLE TO EACH ARTICLE TO BE CONTROLLED AND A READING MEANS FOR EACHOF THE DIVERTES, EACH OF SAID READING MEANS COMPRISING A PHYSICALPATTERN FORMED BY SEVERAL SENSING UNITS FOR SIMULTANEOUSLY SENSING SAIDSEVERAL REFLECTORS OF THE PATTERN, EACH SENSING UNIT INCLUDING A SOURCEOF LIGHT FOR DIRECTING A CONCENTRATED BEAM OF LIGHT TO A PREDETERMINEDONE OF THE REFLECTORS ON THE ARTICLES AND A PHOTOCELL ELECTRICALLYRESPONSIVE TO LIGHT AND POSITIONED TO RECEIVE LIGHT REFLECTED BY THERESPECTIVE PREDETERMINED REFLECTOR ONLY, SAID BEAMS BEING PARALLEL TOEACH OTHER AND TO THE PLANE OF THE CONVEYOR, EACH READING MEANS FURTHERINCLUDING CIRCUIT MEANS CONNECTING THE PHOTOCELLS OF ALL THE SENSINGUNITS FORMING THE PATTERN OF THE RESPECTIVE READING MEANS IN ANENERGIZING CIRCUIT AND AN ELECTRICALLY OPERATED ACTUATING MEANS FOR EACHOF THE DIVERTERS OF THE INSTALLATION, SAID ACTUATING MEANS BEINGCONNECTED TO SAID ENERGIZING CIRCUIT AND OPERATED TO ACTUATE THERESPECTIVE DIVERTER WHEN ALL THE PHOTOCELLS CONNECTED IN THE ENERGIZINGCIRCUIT BECOME SIMULTANEOUSLY ELECTRICALLY RESPONSIVE BY SIMULTANEOUSLYRECEIVING LIGHT REFLECTED FROM THE RESPECTIVE REFLECTORS OF THE PATTERNOF THE REFLECTORS, THE LIGHT REFLECTING SURFACE OF EACH OF SAIDREFLECTORS BEING A RETRODIRECTIVE SURFACE REFLECTING FROM EACH AREAPORTION OF THE SURFACE LIGHT IMPINGING THEREUPON AT ANY ANGLE OFINCIDENCE PARALLEL TO SUCH ANGLE.